String encoding breaks in several edge cases

[ryancdotorg]

The root cause seems to be the string encoder assuming that any character \ud800 is the first half of a well formed UTF-16 surrogate pair. That assumption fails in the following cases:

• Code points U+E000 to U+FFFF
• Unpaired surrogates

JavaScript strings are not necessarily well formed UTF-16. The code needs to process characters in the range \ud800 to \udbff by checking whether they are followed by a character in the range \udc00 to \udfff, and if not, encoding U+FFFD instead. Anything \udc00 to \udfff by itself should also be encoded as U+FFFD.

For example, CBOR.encode("\uff08\u9999\u6e2f\uff09") gives 6bf3928699e6b8aff3929080 rather than the expected 6cefbc88e9a699e6b8afefbc89.

[aaronhuggins]

This is resolved at https://github.com/aaronhuggins/cbor-redux.

[taisukef]

This is resolved at CBOR-es in JavaScript (ES Module) with TextEncoder/TextDecoder
https://github.com/code4fukui/CBOR-es/blob/master/CBOR.js